Positive working resist compositions based on novolac resins are conventionally employed as interlayer insulating films in various electronic parts. Typically, these positive working novolac resin-base resist compositions for interlayer insulating films undergo thermal condensation at temperatures above 200.degree. C. to form insulating films. Volume shrinkage occurs as the treating temperature rises. As a result, hardness increases, but insulation resistance declines. It is thus generally believed that a temperature of about 250.degree. C. and a time of about 10 hours are appropriate for this treatment.
Further improvements in the performance of electronic parts are desired. If the insulating film-forming step involved in the manufacture of such electronic parts requires a treating temperature above 200.degree. C., there is a possibility that metal layers in electronic parts be oxidized or deteriorated. To avoid any influence on metal layers, there is a desire to have an insulating material which can be briefly cured at lower temperature.